<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>let</title>
</head>
<body>
    <script>
        //es6新增的let关键字 用于定义变量
        let a = 6;
        console.log(a)
        //不存在变量提升
        console.log(b)
        let b = 20;
    </script>
</body>
</html>